Pulley holder and a drive transmission mechanism and an image recording apparatus using the pulley holder

Abstract

A pulley holder for rotatably supporting a pulley around which a belt is wound, in which the pulley holder includes a shaft having a shaft body for supporting the pulley and a projection at least one end of the shaft body in its axial direction, and a holder body having a bearing for supporting the shaft body, and a fitting part for fitting the projection. Since the projection is biased from an axis of the shaft body, once the projection is fit into the fitting part, the shaft body would not rotate around the axis. Accordingly, a friction wear of the bearing of the holder body is prevented and thus a shift in conveying a carriage is prevented.

1. A pulley holder for rotatably supporting a pulley around which a belt is to be wound, the pulley holder comprising:
 a shaft including:
 a shaft body that includes a first end portion positioned at a first end thereof, a second end portion positioned at a second end thereof, and a pulley supporting portion positioned between the first end and the second end opposite to the first end in an axial direction of the shaft body, and 
 a projection projecting from the second end of the shaft body in the axial direction of the shaft body and biased from an axis of the shaft body; and 
 
 a holder body having a first groove, a second groove, and a third groove, 
 wherein the first end portion and the second end portion of the shaft body are received by the first groove and the second groove, respectively, and the projection is received by the third groove to prevent the shaft body from rotating with respect to the holder body while allowing the pulley supported by the pulley supporting portion to rotate around the pulley supporting portion, and 
 wherein the shaft body has a cylindrical shape and the projection has a cylindrical shape whose diameter is smaller than the diameter of the shaft body, the axis of the shaft body being parallel with an axis of the projection, 
 wherein the belt wounded around the pulley extends from the pulley in a first direction, and the first groove, the second groove, and the third groove extend in a direction parallel to the first direction and are open at an end of the holder body in a second direction opposite to the first direction, and 
 wherein a groove width of the first groove is substantially the same as a diameter of the first end portion of the shaft body, a groove width of the second groove is substantially the same as a diameter of the second end portion of the shaft body, and a groove width of the third groove is substantially the same as the diameter of the projection. 
 
     
     
       2. The pulley holder as claimed in  claim 1 , wherein the projection is formed into one piece with the shaft body. 
     
     
       3. The pulley holder as claimed in  claim 1 , wherein the shaft is made of metal, and the holder body is made of synthetic resin. 
     
     
       4. The pulley holder as claimed in  claim 3 , wherein the projection is formed into one piece with the shaft body. 
     
     
       5. The pulley holder as claimed in  claim 1 , wherein the holder body is molded using a die. 
     
     
       6. The pulley holder as claimed in  claim 5 , wherein the holder body is angled with a predetermined draft for an easy releasing from the die. 
     
     
       7. The pulley holder as claimed in  claim 1 , wherein the third groove of the holder body is formed continuously from the second groove. 
     
     
       8. The pulley holder as claimed in  claim 1 , wherein the holder body further includes a stopper that narrows the groove width of the third groove and prevents the projection being removed from the third groove. 
     
     
       9. An ink jet type image recording apparatus comprising:
 an ink jet recording head for ejecting ink onto a record medium; 
 a carriage on which the ink jet recording head is mounted; 
 a belt to which the carriage is attached; 
 a first pulley around which the belt is wound and which is connected to a driving source; 
 a second pulley around which the belt is wound and which is arranged at a position spaced from the first pulley by a predetermined distance; and 
 a pulley holder for rotatably supporting the second pulley, the pulley holder including:
 a shaft including:
 a shaft body that includes a first end portion positioned at a first end thereof, a second end portion positioned at a second end thereof, and a pulley supporting portion positioned between the first end and the second end opposite to the first end in an axial direction of the shaft body, and 
 a projection projecting from the second end of the shaft body in the axial direction of the shaft body and biased from an axis of the shaft body; and 
 a holder body having a first groove, a second groove, and a third groove, 
 
 wherein the first end portion and the second end portion of the shaft body are received by the first groove and the second groove, respectively, and the projection is received by the third groove to prevent the shaft body from rotating with respect to the holder body while allowing the pulley supported by the pulley supporting portion to rotate around the pulley supporting portion, and 
 wherein the shaft body has a cylindrical shape and the projection has a cylindrical shape whose diameter is smaller than the diameter of the shaft body, the axis of the shaft body being parallel with an axis of the projection, 
 wherein the belt wounded around the pulley extends from the pulley in a first direction, and the first groove, the second groove, and the third groove extend in a direction parallel to the first direction and are open at an end of the holder body in a second direction opposite to the first direction, and 
 wherein a groove width of the first groove is substantially the same as a diameter of the first end portion of the shaft body, a groove width of the second groove is substantially the same as a diameter of the second end portion of the shaft body, and a groove width of the third groove is substantially the same as the diameter of the projection. 
 
 
     
     
       10. The image recording apparatus as claimed in  claim 9  further comprising a guide rail on which the carriage is placed. 
     
     
       11. The image recording apparatus as claimed in  claim 10 , wherein the guide rail is provided with a hole for receiving the pulley holder. 
     
     
       12. The pulley holder as claimed in  claim 1 , wherein the axis of the projection is biased from the axis of the shaft body by a predetermined distance, and the axis of the projection received by the third groove is spaced away from the axis of the shaft body received by the second groove by the predetermined distance in the first direction. 
     
     
       13. The pulley holder as claimed in  claim 1 , wherein the third groove is formed at a center of the second groove with respect to a groove width direction which is perpendicular to the first direction.